1. Field of the Invention
The present invention relates to a method and device for conducting on-line and real-time spectroreflectometry oxygenation measurement in the eye.
2. Brief Description of the Prior Art
A known prior art method uses a xenon flash, a fundus camera and a CCD (Charge Coupled Device) detector to make spectrographic measurements of the fundus of the eye. The xenon flash illuminates the eye during a short period of time for a single measurement. Due to the high intensity of the xenon light, such measurement could not be repeated on a continuous basis without harming the eye.
For measuring the oxygen content of blood, other prior art methods perform blood flow measurements using Doppler based procedures.
Another prior art method is described in U.S. Pat. No. 4,569,354 (Shapiro et al.) issued on Feb. 11, 1986. In accordance with this method, oxygenation of the retina is determined by measuring the fluorescence of flavoprotein in the retina. A spot of excitation light of a frequency of about 450 nanometers is scanned across the retina. Fluorescent light emitted from the retina at a frequency of about 520 nanometers is detected. The emission light may be detected at two frequencies of about 520 nm and 540 nm to allow for compensation for absorption and transmission variables in the eye. The center of the lens is imaged onto an optical stop in the emission optical path so that emitted light which passes back through the lens periphery, and not fluorescent light from the center of the lens, is detected.
U.S. Pat. No. 5,433,197 granted to Edward W. Stark on Jul. 18, 1995 discloses a glucose sensor for determining blood glucose which is of particular value in the diagnosis and treatment of diabetes. The patient's eye is illuminated with near-infrared radiation which passes into the eye through the cornea and the aqueous humor, is reflected from the iris and/or lens surface, and then passes out through the aqueous humor and cornea. The reflected radiation is collected and detected by a near-infrared sensor which measures the reflected energy in one or more wavelength bands. Comparison of the reflected energy with the source energy provides a measure of the spectral absorption by the eye which is characteristic of the composition of the cornea, the aqueous humor, and the other structures within the eye through which the energy is transmitted or from which it is reflected.
The above prior art shows that need still exists for an efficient method and device for performing on-line and real-time oxygenation measurement in the eye.